In tungsten-halogen lamps, the deposition of evaporated tungsten deposits on the envelope wall is reduced or retarded by the regenerative action of the halogen cycle, which operates by virtue of the temperature gradient between the filament and the bulb. As a general concept:                a. The filament, fill gas, and bulb are initially at some low temperature (e.g., ambient, for a cold start).        b. When power is applied, the filament rapidly rises to its operating temperature (2800K to 3400K depending on application), heating the fill gas and the bulb. The bulb wall rises to an operating temperature of 400° C. to 1000° C., and the fill gas rises to temperatures ranging from that at the filament to that at the bulb wall. This temperature gradient causes convection currents in the fill gas.        c. As the bulb wall rises above temperatures in the range 200° C. to 250° C. (depending on nature and amount of halogen vapor), the halogen cycle begins to operate. Tungsten molecules evaporated from the filament combine with the halogen vapor to form a tungsten halide (e.g., tungsten iodide or tungsten bromide). The halide does not condense on the hot wall of the bulb but is circulated by convection back to the region of the filament.        d. At the filament where the temperature exceeds 2500° C., the tungsten halide dissociates, the tungsten is deposited on the filament, and        e. The free halogen vapor is recirculated to continue the regenerative cycle. This cycle thus keeps the bulb wall clean by preventing deposition of tungsten and results in much higher lumen maintenance over the life of the lamp than that obtained for conventional tungsten-filament lamps.        
PAR lamps typically comprise a light source such, for example, as a tungsten halogen capsule comprised of quartz or a hard glass, mounted in a pressed borosilicate glass body having a reflective coating applied to the inner surface of the body. A pressed glass lens usually covers the front aperture of the body and may contain optical elements to give a desired beam shape, for example, a spot or flood configuration. General service PAR lamps typically have a medium screw base attached to the body for electrical connection to 100V to 240V circuits. In many T-H PAR lamps the hard glass capsule contains stiff electrical lead-ins that connect to the relatively deformable inner leads of the light source and that are themselves pressed into the seal area of the capsule. Such capsules are shown in U.S. Pat. No. 5,660,462, Bockley, et al., and U.S. Published Patent Applications 2005/0212396 A1, Oetken, et al. and 2006/0043890 A1, Kling (all of which are assigned to the assignee of the instant invention). Often, in such lamps the capsule is supported by crimping the leads into metal eyelets that are formed in the base of the envelope body.
Problems arise in the sealing of the heavy metal lead-ins into the glass. The differences in thermal expansion of the heavy metal lead-ins and the glass eventually causes cracking problems that shorten the life of the lamps. While numerous metal alloys have been developed to attempt to match, within a critical range, the thermal expansion of the glass, these alloys themselves are expensive and, sometimes, difficult to work with.
Another technique that has been employed utilizes additional parts such as a metal disc that fastens to the capsule and centers it in the neck of the envelope body. Such a technique is shown in U.S. Pat. No. 5,751,095, Zalar, which also employs multiple glass or ceramic insulators to guide the lead-ins to the screw base.
It would be an advance in the art to provide a simple and inexpensive way to mount a single ended hard glass capsule with deformable, flexible lead-ins into a hard glass reflector.